One of the first steps in a fusion procedure on a damaged bone joint is to prepare the surface of the bone ends for optimal engagement. Most commonly, the bone ends are sawed, and/or finished smooth, so as to be flat to create opposing planar surfaces that mate to form an angled miter-type joint. In cutting the bone ends to form this joint, the surgeon typically uses a flat reciprocating saw blade. A template or saw guide is also commonly used to align the blade to cut at the precise angle required.
Of particular interest with respect to creating such miter-type joints in a digit is illustrated as a part of the Joint Fixation System and Related Method, set forth in Applicant's co-pending U.S. Patent application, Combs, Ser. No. 08/510,721, filed Aug. 3, 1995, pending. In this prior application, I have illustrated and claimed a method and related surgical instruments/tools for preparing and stabilizing a joint in the finger or toe for fusion. More specifically, the instruments include a saw guide with linear guide slots for aligning a flat, reciprocating saw blade to make a planar cut on the end of the bone, such as the middle phalanx of the finger. This prior application thus addresses the need for a system and method of making flat cuts on the small bones of a digit.
Especially with a joint of a digit, such as the middle/distal phalanx joint in a finger, it is desirable in certain situations to form the end of one member of the joint into a rounded/spherical shape. This option is particularly favored to provide a better match between the two bones forming the joint. Also, providing a rounded end surface to at least one member, the opposing member may be positioned at the optimum angle for fusion. For example, when the first finger is being surgically repaired, the surgeon is able to select the best angle to provide maximum use with the thumb, such as to grasp and pick up items.
In the prior art, there are several surgical instruments, predominantly rotary milling tools/reamers that are specifically designed for cutting/smoothing the end of a large bone, such as the femur. These prior art tools are typically concave or cup-shaped with cutting protrusions on their outer edge and within their generally hemispherical interior to produce a full spherical or ball shape bone end.
One disadvantage with these tools is that their continuous hemispherical shape prevents them from accessing the bone end in its natural position. Instead, the bone must be severely dislocated to allow the end to be inserted into the cutting recess. This additional step of dislocating the bone increases both the complexity and the overall required time for the preparatory procedure for fusion. An example of a typical cup-shaped cutting tool is shown in U.S. Pat. No. 4,284,080 to Rehder, and a similar cutting tool is shown in U.S. Pat. No. 3,667,456 to Charnley.
Another disadvantage with the prior art surgical cutting instruments and tools for rounding a bone end is that none are designed to be used with a guide or template. As explained above, the saw guides of the prior art are designed solely for aligning flat, linearly reciprocating saw blades to make single plane cuts at a fixed angle. None of the prior art saw guides are designed for or capable of making multi-plane, rounded/spherical cuts. Examples of typical prior art saw guides are the U.S. patents to Johnson U.S. Pat. No. 4,718,413 and Rayhack U.S. Pat. No. 5,176,685.
Currently, the most common method for cutting the end of a small bone, such as the middle phalanx, into a mating shape is to use a reciprocating flat blade in a hand piece assembly. Generally, only substantially single plane, linear cuts can be reliably obtained to shape the bone end. This technique is very tedious and time-consuming, as the surgeon must slowly and carefully remove small shavings of the bone to insure that the proper angle and shape is obtained and that the bone is not unduly shortened. Without any external alignment or guidance, in real life it is inevitable that misshapen and unsymmetrical bone ends are often created. Furthermore, because the surgeon is manipulating the saw free-hand, slips of the blade and inadvertent cuts of delicate surrounding tissue are a constant possibility.
Thus, as demonstrated by the limitations of the prior art, there is a need identified for a multi-plane curvilinear saw, corresponding guide and related method that are specifically designed for cutting the ends of the small bones in the fingers or toes. This allows the surgeon to accurately, efficiently and safely perform the cutting procedure so as to provide a more efficient match of the bone ends.